F5A Head Chamber Volume.

[Tez]

A knowledgeable friend of mine was asking after the figure - he wants to calculate the ACTUAL compression I have (rather than the published compression).

This is a very geeky question but someone might have it documented somewhere.

Can anybody tell me what the chamber volume per cylinder is in the HEAD of a standard F5A motor?

Hoping someone has the figure.

Cheers...

[Al_Zhiemer]

Get the head sitting level, seal the valves so they can't leak, get a good syringe with 1 millilitre increments and start filling up the chamber with water until the water level sits flush with surface of the head. this will give you an approximate measurement to work off and then convert it in to what ever unit of measurement you want to use.

just make sure you dry the head of properly afterwards.

[Ralf the RR]

A knowledgeable friend of mine was asking after the figure - he wants to calculate the ACTUAL compression I have (rather than the published compression).

Surely the published figure is close enough, unless there has been some modifications (head shaved, block decked, different pistons, different head gasket, different rods, different crank, etc)

I don't know how accurate you want to be, but there is more to the compression ratio than head volume.

Compression ratio is defined as (Swept Volume + Clearance Volume)/(Clearance volume)

Swept volume = Pi * (bore/2)^2 * stroke
Clearance volume = combustion chamber volume + piston deck volume + head gasket volume.
There are things to consider when measuring this volume. Dish/Domed piston, valve reliefs, ring land volume, head gasket volume.

Also, each combustion chamber volume might be slightly different, that's why they cc heads!

Remember that a worn engine still has the same compression ratio as a new engine (well close enough), however the compression (psi) may be down.